With the growth of mobile communication, in order to provide in-building and outdoor wireless service, mobile operators use small cells to extend their service coverage and increase network capacity. Small cells may be radio access nodes, for example, having a range of 10 meters to 2 kilometers, as compared to a macrocell, for example, having a range of a few tens of kilometers. Examples of small cells include femtocells, picocells, and microcells. In 3rd Generation Partnership Project (3GPP) terminology, a Node B (NB) is a 3G macrocell, an eNode B (eNB) is a Long Term Evolution (LTE) macrocell, a Home Node B (HNB) is a 3G femtocell, and a Home eNode B (HeNB) is a LTE femtocell.
As wireless networks become increasingly dense to accommodate the rising traffic demand, inter-cell interference becomes one of the critical issues. Specifically, with an increasing number of small cells, deployment of small cells becomes denser and thus the distance between small cells becomes shorter. A user equipment (UE), such as a mobile phone, served by a serving cell may suffer from interference caused by a neighboring small cell. For example, when UE is near boundary of the serving cell, signal from neighboring cell acts as interferer. The Signal-to-Noise ratio (SNR) may be poor not only because of the weak signal strength from the serving cell but also because of the interference. Thus, there is a need for a method for interference coordination.